This sample chapter from CCNP Support Exam Certification Guide introduces some powerful troubleshooting tools that are built into the Cisco IOS. As with other tools, it is important that you identify when to use them and what information they reveal. Because some of these tools have an impact on the way routers operate and may impede the routers' utmost performance, it is essential to use them with care. To better understand the output of these commands, and to recognize what router internal operations they affect, this chapter discusses router internal components and operations. As each tool/command is introduced, its usefulness is described and tips are given on how to use it effectively.

This chapter is from the book

This chapter is from the book

The Cisco IOS troubleshooting commands help you gather valuable information
about the state of the network and its devices. The gathered facts help
eliminate some of the possibilities, at the same time strengthening the
likelihood of the hypotheses that you may have formed. Again, due to the impact
that certain troubleshooting commands (debug, for example) have on some of the
router's internal operationsand ultimately on the router's
performancethese commands have to be used selectively, properly, and
temporarily.

"Do I Know This Already?" Quiz

If you wish to evaluate your knowledge of the contents of this chapter before
you get started, answer the following questions. The answers are provided in
Appendix A, "Answers to Quiz Questions." If you are having difficulty
providing correct answers, you should thoroughly review the entire chapter. If
all or most of your answers are correct, you might want to skim this chapter for
only those subjects you need to review. You can also use the "Foundation
Summary" section to quickly review topics. Once you have completed the
chapter, you should reevaluate yourself with the questions in the
"Q&A" section at the end. Finally, use the companion CD-ROM to
evaluate your knowledge of the topics and see if you need a review.

Which of the route caching methods are not enabled by default?
And from which configuration mode (prompt level) can they be enabled?

With regard to speed and switching optimization, how did Cisco
Systems improve the Cisco 7500 routers (in comparison to the 7000
series)?

Briefly describe the advantages of Netflow switching. Also
specify whether there should be any precautions with respect to enabling Netflow
switching.

Provide at least three examples of operations or packet types
that are process switched.

Before you activate Debug, what are some of its characteristics
that you should consider?

Before you enable debugging on a router, you are encouraged to
check the router's CPU utilization. What is the command that allows you to
do that? If the utilization is above 50%, are you encouraged to debug packets or
to debug events?

What is the default setting (for example, enabled/disabled,
default destination) for message logging?

What information does the output of the show logging Cisco
IOS exec command display?

The outputs of the show memory and the show processes
[cpu] commands will most likely be asked for in which situation (loss of
functionality, crash, or performance degradation)?

If the output of show buffer command displays a large
number of misses, increasing the value of which one of the buffer management
parameters (Permanent, Min-Free, Max-Free, Initial) will most likely remedy the
situation?

The show processes command's output provides two
numbers separated by a slash (for example, 4%/4%) for the CPU utilization over
the last five seconds. How are those numbers interpreted?

Which command causes the router to attempt to produce a core dump
when it crashes?